/*
   *	xt_conntrack - Netfilter module to match connection tracking
   *	information. (Superset of Rusty's minimalistic state match.)

   *

   *	(C) 2001  Marc Boucher (marc@mbsi.ca).

   *	(C) 2006-2012 Patrick McHardy <kaber@trash.net>

   *	Copyright © CC Computer Consultants GmbH, 2007 - 2008

   *

   *	This program is free software; you can redistribute it and/or modify
   *	it under the terms of the GNU General Public License version 2 as
   *	published by the Free Software Foundation.

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/module.h>
  #include <linux/skbuff.h>

  #include <net/ipv6.h>

  #include <linux/netfilter/x_tables.h>
  #include <linux/netfilter/xt_conntrack.h>

  #include <net/netfilter/nf_conntrack.h>

  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");

  MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");

  MODULE_DESCRIPTION("Xtables: connection tracking state match");

  MODULE_ALIAS("ipt_conntrack");

  MODULE_ALIAS("ip6t_conntrack");

  static bool

  conntrack_addrcmp(const union nf_inet_addr *kaddr,
                    const union nf_inet_addr *uaddr,
                    const union nf_inet_addr *umask, unsigned int l3proto)
  {

  	if (l3proto == NFPROTO_IPV4)

  		return ((kaddr->ip ^ uaddr->ip) & umask->ip) == 0;

  	else if (l3proto == NFPROTO_IPV6)

  		return ipv6_masked_addr_cmp(&kaddr->in6, &umask->in6,
  		       &uaddr->in6) == 0;
  	else
  		return false;
  }
  
  static inline bool
  conntrack_mt_origsrc(const struct nf_conn *ct,

                       const struct xt_conntrack_mtinfo2 *info,

  		     u_int8_t family)

  {
  	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
  	       &info->origsrc_addr, &info->origsrc_mask, family);
  }
  
  static inline bool
  conntrack_mt_origdst(const struct nf_conn *ct,

                       const struct xt_conntrack_mtinfo2 *info,

  		     u_int8_t family)

  {
  	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3,
  	       &info->origdst_addr, &info->origdst_mask, family);
  }
  
  static inline bool
  conntrack_mt_replsrc(const struct nf_conn *ct,

                       const struct xt_conntrack_mtinfo2 *info,

  		     u_int8_t family)

  {
  	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3,
  	       &info->replsrc_addr, &info->replsrc_mask, family);
  }
  
  static inline bool
  conntrack_mt_repldst(const struct nf_conn *ct,

                       const struct xt_conntrack_mtinfo2 *info,

  		     u_int8_t family)

  {
  	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3,
  	       &info->repldst_addr, &info->repldst_mask, family);
  }

  static inline bool

  ct_proto_port_check(const struct xt_conntrack_mtinfo2 *info,

                      const struct nf_conn *ct)
  {
  	const struct nf_conntrack_tuple *tuple;
  
  	tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
  	if ((info->match_flags & XT_CONNTRACK_PROTO) &&

  	    (nf_ct_protonum(ct) == info->l4proto) ^

  	    !(info->invert_flags & XT_CONNTRACK_PROTO))
  		return false;
  
  	/* Shortcut to match all recognized protocols by using ->src.all. */
  	if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
  	    (tuple->src.u.all == info->origsrc_port) ^
  	    !(info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
  		return false;
  
  	if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
  	    (tuple->dst.u.all == info->origdst_port) ^
  	    !(info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
  		return false;
  
  	tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  
  	if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
  	    (tuple->src.u.all == info->replsrc_port) ^
  	    !(info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
  		return false;
  
  	if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
  	    (tuple->dst.u.all == info->repldst_port) ^
  	    !(info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
  		return false;
  
  	return true;
  }

  static inline bool
  port_match(u16 min, u16 max, u16 port, bool invert)
  {
  	return (port >= min && port <= max) ^ invert;
  }
  
  static inline bool
  ct_proto_port_check_v3(const struct xt_conntrack_mtinfo3 *info,
  		       const struct nf_conn *ct)
  {
  	const struct nf_conntrack_tuple *tuple;
  
  	tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
  	if ((info->match_flags & XT_CONNTRACK_PROTO) &&
  	    (nf_ct_protonum(ct) == info->l4proto) ^
  	    !(info->invert_flags & XT_CONNTRACK_PROTO))
  		return false;
  
  	/* Shortcut to match all recognized protocols by using ->src.all. */
  	if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
  	    !port_match(info->origsrc_port, info->origsrc_port_high,
  			ntohs(tuple->src.u.all),
  			info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
  		return false;
  
  	if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
  	    !port_match(info->origdst_port, info->origdst_port_high,
  			ntohs(tuple->dst.u.all),
  			info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
  		return false;
  
  	tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  
  	if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
  	    !port_match(info->replsrc_port, info->replsrc_port_high,
  			ntohs(tuple->src.u.all),
  			info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
  		return false;
  
  	if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
  	    !port_match(info->repldst_port, info->repldst_port_high,
  			ntohs(tuple->dst.u.all),
  			info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
  		return false;
  
  	return true;
  }

  static bool

  conntrack_mt(const struct sk_buff *skb, struct xt_action_param *par,

               u16 state_mask, u16 status_mask)

  {

  	const struct xt_conntrack_mtinfo2 *info = par->matchinfo;

  	enum ip_conntrack_info ctinfo;
  	const struct nf_conn *ct;
  	unsigned int statebit;
  
  	ct = nf_ct_get(skb, &ctinfo);

  	if (ct) {
  		if (nf_ct_is_untracked(ct))
  			statebit = XT_CONNTRACK_STATE_UNTRACKED;
  		else
  			statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
  	} else

  		statebit = XT_CONNTRACK_STATE_INVALID;
  
  	if (info->match_flags & XT_CONNTRACK_STATE) {
  		if (ct != NULL) {
  			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
  				statebit |= XT_CONNTRACK_STATE_SNAT;
  			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
  				statebit |= XT_CONNTRACK_STATE_DNAT;
  		}

  		if (!!(state_mask & statebit) ^

  		    !(info->invert_flags & XT_CONNTRACK_STATE))
  			return false;
  	}
  
  	if (ct == NULL)
  		return info->match_flags & XT_CONNTRACK_STATE;

  	if ((info->match_flags & XT_CONNTRACK_DIRECTION) &&
  	    (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) ^

  	    !(info->invert_flags & XT_CONNTRACK_DIRECTION))

  		return false;
  
  	if (info->match_flags & XT_CONNTRACK_ORIGSRC)

  		if (conntrack_mt_origsrc(ct, info, par->family) ^

  		    !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
  			return false;
  
  	if (info->match_flags & XT_CONNTRACK_ORIGDST)

  		if (conntrack_mt_origdst(ct, info, par->family) ^

  		    !(info->invert_flags & XT_CONNTRACK_ORIGDST))
  			return false;
  
  	if (info->match_flags & XT_CONNTRACK_REPLSRC)

  		if (conntrack_mt_replsrc(ct, info, par->family) ^

  		    !(info->invert_flags & XT_CONNTRACK_REPLSRC))
  			return false;
  
  	if (info->match_flags & XT_CONNTRACK_REPLDST)

  		if (conntrack_mt_repldst(ct, info, par->family) ^

  		    !(info->invert_flags & XT_CONNTRACK_REPLDST))
  			return false;

  	if (par->match->revision != 3) {
  		if (!ct_proto_port_check(info, ct))
  			return false;
  	} else {
  		if (!ct_proto_port_check_v3(par->matchinfo, ct))
  			return false;
  	}

  	if ((info->match_flags & XT_CONNTRACK_STATUS) &&

  	    (!!(status_mask & ct->status) ^

  	    !(info->invert_flags & XT_CONNTRACK_STATUS)))
  		return false;
  
  	if (info->match_flags & XT_CONNTRACK_EXPIRES) {
  		unsigned long expires = 0;
  
  		if (timer_pending(&ct->timeout))
  			expires = (ct->timeout.expires - jiffies) / HZ;
  		if ((expires >= info->expires_min &&
  		    expires <= info->expires_max) ^
  		    !(info->invert_flags & XT_CONNTRACK_EXPIRES))
  			return false;
  	}
  	return true;
  }

  static bool

  conntrack_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)

  {

  	const struct xt_conntrack_mtinfo1 *info = par->matchinfo;

  	return conntrack_mt(skb, par, info->state_mask, info->status_mask);
  }
  
  static bool

  conntrack_mt_v2(const struct sk_buff *skb, struct xt_action_param *par)

  {
  	const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
  
  	return conntrack_mt(skb, par, info->state_mask, info->status_mask);

  }

  static bool
  conntrack_mt_v3(const struct sk_buff *skb, struct xt_action_param *par)
  {
  	const struct xt_conntrack_mtinfo3 *info = par->matchinfo;
  
  	return conntrack_mt(skb, par, info->state_mask, info->status_mask);
  }

  static int conntrack_mt_check(const struct xt_mtchk_param *par)

  {

  	int ret;
  
  	ret = nf_ct_l3proto_try_module_get(par->family);

  	if (ret < 0)

  		pr_info("cannot load conntrack support for proto=%u
  ",
  			par->family);

  	return ret;

  }

  static void conntrack_mt_destroy(const struct xt_mtdtor_param *par)

  {

  	nf_ct_l3proto_module_put(par->family);

  }

  static struct xt_match conntrack_mt_reg[] __read_mostly = {
  	{
  		.name       = "conntrack",

  		.revision   = 1,

  		.family     = NFPROTO_UNSPEC,

  		.matchsize  = sizeof(struct xt_conntrack_mtinfo1),

  		.match      = conntrack_mt_v1,

  		.checkentry = conntrack_mt_check,
  		.destroy    = conntrack_mt_destroy,

  		.me         = THIS_MODULE,
  	},
  	{
  		.name       = "conntrack",
  		.revision   = 2,
  		.family     = NFPROTO_UNSPEC,
  		.matchsize  = sizeof(struct xt_conntrack_mtinfo2),

  		.match      = conntrack_mt_v2,

  		.checkentry = conntrack_mt_check,
  		.destroy    = conntrack_mt_destroy,
  		.me         = THIS_MODULE,
  	},

  	{
  		.name       = "conntrack",
  		.revision   = 3,
  		.family     = NFPROTO_UNSPEC,
  		.matchsize  = sizeof(struct xt_conntrack_mtinfo3),
  		.match      = conntrack_mt_v3,
  		.checkentry = conntrack_mt_check,
  		.destroy    = conntrack_mt_destroy,
  		.me         = THIS_MODULE,
  	},

  };

  static int __init conntrack_mt_init(void)

  {

  	return xt_register_matches(conntrack_mt_reg,
  	       ARRAY_SIZE(conntrack_mt_reg));

  }

  static void __exit conntrack_mt_exit(void)

  {

  	xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));

  }

  module_init(conntrack_mt_init);
  module_exit(conntrack_mt_exit);